All-cause mortality after self-reported vs. hospital-reported gynecological surgery: The HUNT study

The impact of hysterectomy and bilateral oophorectomy on future mortality risk is still debated. Self-reported exposure may be a major source of bias in many studies. We aimed to determine mortality following hospital-reported hysterectomy and bilateral oophorectomy and compare to results based on self-reported surgeries.

We included 37 140 women from the second (1995-1997) and third (2006-2008) HUNT surveys. HUNT (the Trøndelag Health Study) is a population-based Norwegian cohort study, and we linked to the Norwegian Cause of Death Registry, the Cancer Registry of Norway, and hospital surgical codes. The participants were followed from inclusion in HUNT until December 2020. Women were classified as unexposed, exposed to hysterectomy alone, exposed to bilateral oophorectomy alone, or exposed to both surgeries. Hospital-reported exposure was determined using surgical procedure codes, whereas self-reported exposure was obtained from the HUNT questionnaires. To be classified as exposed based on self-report, a woman had to indicate that she had undergone the surgery and provide her age at the time of the procedure. We compared the hazard of death in unexposed vs. exposed groups using Cox regression analysis, adjusting for relevant covariates.

Compared with unexposed women, hospital-reported hysterectomy was associated with a reduced hazard of death (HR 0.72 [95% CI 0.62-0.84]), while self-reported hysterectomy showed no association (HR 1.06 [95% CI 0.97-1.16]). For bilateral oophorectomy, hospital-reported cases showed an HR of 0.83 (95% CI 0.64-1.07), while self-reported cases indicated an HR of 1.14 (95% CI 0.97-1.33). Women who had both hysterectomy and bilateral oophorectomy demonstrated no significant association with mortality, regardless of whether the surgeries were hospital-reported (HR 1.13 [95% CI 0.96-1.34]) or self-reported (0.93 [95% CI 0.82-1.06]). Early hospital-reported bilateral oophorectomy was associated with an increased hazard of death, particularly when performed before the age of 50.

Results differed between hospital-reported and self-reported exposure. This could explain the heterogeneity observed in previous studies on mortality risk after hysterectomy and oophorectomy. In this study, hospital-reported hysterectomy and bilateral oophorectomy were not associated with increased mortality, whereas early bilateral oophorectomy was.